Reliability of maintained ship hull girders subjected to corrosion and fatigue

A formulation is presented to account for the effect of corrosion and fatigue on the reliability of ship hulls. A time variant formulation is presented in which the effect of these degradation phenomena on the hull section modulus is quantified. The effect of maintenance actions is accounted for by considering that the repaired elements are restored to a state as new. Different repair policies can be studied and the approach can be used as a tool to plan the maintenance actions based on reliability results.     

Carbon nanotubes based optical immunodetection of Staphylococcal Enterotoxin B (SEB) in food

Staphylococcal enterotoxins (SEs) are a major cause of food-borne diseases, traditionally SEs assayed immunologically with ELISA. Carbon nanotubes' (CNT) unique mechanical and electronic properties combined with a large specific surface area make them attractive for biosensing. To investigate whether CNT could improve the sensitivity of ELISA assays, we developed an optical CNT immunosensor for the detection of Staphylococcal Enterotoxin B (SEB) in food. Anti-SEB antibodies were immobilized onto a CNT surface through electrostatic adsorption and then the antibody-nanotube mixture was bound onto a polycarbonate film. SEB was then detected by a "sandwich-type" ELISA assay on the polycarbonate film. The use of CNT increased the sensitivity of the immunosensor by at least 6-fold, lowering the detection limit of SEB. The CNT immunosensor was also able to detect SEB various foods, suggesting the utility of CNT for this and other optical-based immunological detection methods.     

Low-cost plastic plasmonic substrates for operation in aqueous environments

We report a novel design of a multilayer stack to attain surface-plasmon-coupled emission (SPCE) enhancements in liquid medium. Variation in thickness of the multilayer affects the position and depth of resonance plasmon dips. Numerical investigation resulted in an optimal stack configuration that supports long-range surface plasmons. SPCE substrates were prepared on plain BK7 glass and Teflon-AF coated polycarbonate (PC-T) substrates by modifying their surface functionalities using plasma etching. The changes in refractive indices due to the presence of the fluoropolymer layer help reduce the SPCE exit angle from α = 75° (plain BK7) to α = 60° (PC-T) in water without requiring specialized optics.     

Signal enhancement of surface plasmon-coupled directional emission by a conical mirror

A simple strategy for increasing the collection efficiency of surface plasmon-coupled emission (SPCE) is demonstrated. SPCE is a near-field phenomenon occurring when excited fluorophores are in close proximity to a subwavelength metal film. The energy of the fluorophores induces surface plasmons that radiate the coupled energy at highly specific angles. In an attempt to maximize the collected emission, a conical mirror was placed around the coupling prism. The result was a nearly 500 fold enhancement over the free space signal as detected from a single point from a poly(vinyl alcohol) layer doped with ruthenium. Coupling this large enhancement with LED excitation could lead to the development of inexpensive, handheld fluorescent devices with high sensitivity.     

Process integration and nanometer-scale electrical characterization of crystalline high-k gate dielectrics

Crystalline praseodymium oxide (Pr₂O₃) high-k gate dielectric has been successfully integrated into a polysilicon gate CMOS technology. Fully functional MOSFETs with an equivalent oxide thickness (EOT) of 1.8 nm and gate leakages below 10⁻⁶ A/cm² have been fabricated. However, at this early stage of development the transistors show Vt-instabilities and unusual high gate leakage for L > 10 μm. As a first attempt to explain the observed macroscopic device characteristics, topographical and electrical measurements at the nanometer scale have been performed directly on the Pr₂O₃ surface by Conductive Atomic Force Microscopy (C-AFM). This technique allows to discriminate between structural defect sites and charge trapping centers.     

Ratio measurements in oxygen determinations: wavelength ratiometry, lifetime discrimination, and polarization detection

In this work we present ratiometric measurements of oxygen concentrations using a dual-emitting dye. Three different methods for ratio measurements in oxygen sensing are employed. The standard wavelength-ratiometric approach is simple to implement, but the sensor response has significant non-linearity. The frequency discrimination of the lifetimes allows for measurements of dual-emission ratio through a single emission filter. In this case the Stern–Volmer plots are linear. Another option is to use emission polarization.     

Fluorescence imaging of electrical activity in cardiac cells using an all-solid-state system

Tracking spatial and temporal determinants of cardiac arrhythmogenesis at the cellular level presents challenges to the optical mapping techniques employed. In this paper, we describe a compact system combining two nontraditional low-cost solutions for excitation light sources and emission filters in fluorescence measurements of transmembrane potentials, Vm, or intracellular calcium, [Ca2+]i in cardiac cell networks. This is the first reported use of high-power blue and green light emitting diodes (LEDs), to excite cell monolayers stained with Vm - (di-8-ANEPPS) or [Ca2+]i - (Fluo-3) sensitive dyes. In addition, we use simple techniques for fabrication of suitable thin emission filters with uniform properties, no auto-fluorescence, high durability and good flexibility for imaging Vm or [Ca2+]i. The battery-operated LEDs and the fabricated emission filters, integrated with a fiber-optic system for contact fluorescence imaging, were used as tools to characterize conduction velocity restitution at the macro-scale. The versatility of the LEDs for illumination is further emphasized through 1) demonstration of their usage for epi-illumination recordings at the single-cell level, and 2) demonstration of their unique high-frequency light modulation ability. The LEDs showed excellent stability as excitation light sources for fluorescence measurements; acceptable signal-to-noise ratio and negligible cell photodamage and indicator dye photobleaching were observed.     

Carbon nanotubes with enhanced chemiluminescence immunoassay for CCD-based detection of Staphylococcal enterotoxin B in food

Enhanced chemiluminescence (ECL) detection can significantly enhance the sensitivity of immunoassays but often requires expensive and complex detectors. The need for these detectors limits broader use of ECL in immunoassay applications. To make ECL more practical for immunoassays, we utilize a simple cooled charge-coupled device (CCD) detector combined with carbon nanotubes (CNTs) for primary antibody immobilization to develop a simple and portable point-of-care immunosensor. This combination of ECL, CNT, and CCD detector technologies is used to improve the detection of Staphylococcal enterotoxin B (SEB) in food. Anti-SEB primary antibodies were immobilized onto the CNT surface, and the antibody-nanotube mixture was immobilized onto a polycarbonate surface. SEB was then detected by an ELISA assay on the CNT-polycarbonate surface with an ECL assay. SEB in buffer, soy milk, apple juice, and meat baby food was assayed with a LOD of 0.01 ng/mL using our CCD detector, a level similar to the detection limit obtained with a fluorometric detector when using the CNTs. This level is far more sensitive than the conventional ELISA, which has a LOD of approximately 1 ng/mL. Our simple, versatile, and inexpensive point-of-care immunosensor combined with the CNT-ECL immunoassay method described in this work can also be used to simplify and increase sensitivity for many other types of diagnostics and detection assays.     

Process damage-free damascene metal gate technology for gentle integration of epitaxially grown high-k

This paper presents the first successful attempt to integrate crystalline high-k gate dielectrics into a virtually damage-free damascene metal gate process. Process details as well as initial electrical characterization results on fully functional gate Gd₂O₃ dielectric MOSFETs with equivalent oxide thickness (EOT) down to 1.9 nm are discussed and compared with devices with rare-earth gate dielectrics fabricated previously in a conventional CMOS process.     

A simple 96 well microfluidic chip combined with visual and densitometry detection for resource-poor point of care testing

There is a well-recognized need for low cost biodetection technologies for resource-poor settings with minimal medical infrastructure. Lab-on-a-chip (LOC) technology has the ability to perform biological assays in such settings. The aim of this work is to develop a low cost, high-throughput detection system for the analysis of 96 samples simultaneously outside the laboratory setting. To achieve this aim, several biosensing elements were combined: a syringe operated ELISA lab-on-a-chip (ELISA-LOC) which integrates fluid delivery system into a miniature 96-well plate; a simplified non-enzymatic reporter and detection approach using a gold nanoparticle-antibody conjugate as a secondary antibody and silver enhancement of the visual signal; and carbon nanotubes (CNT) to increase primary antibody immobilization and improve assay sensitivity. Combined, these elements obviate the need for an ELISA washer, electrical power for operation and a sophisticated detector. We demonstrate the use of the device for detection of Staphylococcal enterotoxin B, a major foodborne toxin using three modes of detection, visual detection, CCD camera and document scanner. With visual detection or using a document scanner to measure the signal, the limit of detection (LOD) was 0.5 ng/ml. In addition to visual detection, for precise quantitation of signal using densitometry and a CCD camera, the LOD was 0.1 ng/ml for the CCD analysis and 0.5 ng/ml for the document scanner. The observed sensitivity is in the same range as laboratory-based ELISA testing. The point of care device can analyze 96 samples simultaneously, permitting high throughput diagnostics in the field and in resource poor areas without ready access to laboratory facilities or electricity.